1.
1
Do nothing. The chlorine will eventually drop to the desired level. High amounts of sunlight and a high bather load will speed up the process.

2.
2
You can add chemicals to the water. Sodium Thiosulfate and Sodium Sulfite are the most common. Pool stores can order industrial Sodium Thiosulfate in a large bag. Commercial chorine neutralizer is the same thing except in a pretty small bottle and many times more expensive. Another possibility is peroxide. Pool stores carry peroxide in 5gal jugs for UV sanitation systems. Either way be careful not to add too much; if you do, it may be very hard to maintain a proper chlorine level for some time, the residual in the water will keep taking the chlorine down.
3.
3
Replace some of the pool water with fresh water. This solution will also have the positive side-effect of lowering total dissolved solids and cyanuric acid.